1. Technical Field
The present invention relates in general to the field of electronics, and in particular to the removal of extraneous heat from electronic chips. More particularly, the present invention relates to a functional design and method of manufacture of a heat sink having a heatpipe.
2. Description of the Related Art
In a typical personal computer (PC), the main heat-generating component among the logic circuits is the processor, also referred to as the Central Processing Unit (CPU) or microprocessor (MP). As illustrated in FIG. 1a, a processor 102 is mounted in a socket 104, which is mounted on a (printed) circuit board 106, by mating pins 108 from the processor 102 into the socket 104. As processors continue to grow in performance, so does the heat generated by the processors. This heat, if excessive, can cause the processor 102, or any other similar Integrated Circuit (IC) package, to malfunction or fail entirely.
To remove heat from processor 102, a heat sink (HS) 110, having a HS base 112 and a plurality of fins 114, is secured to processor 102 by a strap 116 or other attachment means. Heat is conducted from the processor 102 to the HS base 112 and the fins 114, which dissipate heat by conduction and convection to ambient air surrounding fins 114. To provide thermal conduction between a top surface 120 of processor 102 and the HS base 112, a thermal grease 118, typically a thermally conductive silicon or filled hydrocarbon grease doped with fillings such as metals, is used.
A major problem with the heat sink 110 shown in FIG. 1a is that it relies on conduction to the ambient air, which may or may not be moving enough to significantly convey away heat, depending on movement of air about the heat sink caused by fan(s) in a computer case that houses the processor 102. To aid in this air movement, the prior art provided the improvement of a heat sink fan 122, as shown in FIG. 1b. As shown, heat sink fan 122 includes fan blades 124 that rotate about a hub 126.
As IC's became even denser with more and more transistors and other electronic components, the heat sink configurations shown in FIGS. 1a–b became insufficient to remove damaging heat from IC packages such as that shown for processor 102. The next step-up in prior art heat removal technology was the development of a heat sink that incorporated a pipe filled with a heat-transferring fluid. This type of heat sink is known as a “heatpipe.” With reference now to FIG. 2a, a prior art heatpipe 200 is depicted. Heatpipe 200 is composed of a heatpipe base 202, which is adjacent to processor 102, with or without intermediary thermal grease 118. As shown in FIGS. 2a–c, attached to heatpipe base 202 is a pipe 204, from which a plurality of horizontal fins 206 extends. Horizontal fins 206 convectively remove heat away from pipe 204, in a manner similar to that described for fins 114 described in FIGS. 1a–b. However, heatpipe 200 utilizes fluid heat transfer as well.
As shown in FIG. 2c, pipe 204 is filled with a fluid 208, which is retained inside of pipe 204 by a pipe cap 210. As depicted by the flow arrows in FIG. 2c, fluid 208 circulates in a vertical manner within pipe 204. That is, as fluid 208 is heated at the bottom of pipe 204, which is adjacent heatpipe base 202 and thus the heat producing processor 102, fluid 208 rises upwards towards a pipe cap 210 at the top of pipe 204. When fluid 208 reaches pipe cap 210, fluid 208 flows back down the interior sides of pipe 204. The sides of pipe 204 are able to conduct away heat from fluid 208, since the horizontal fins 206 provide additional conduction/convection cooling from the sides of pipe 204 to the ambient air.
While the heatpipe 200 depicted in FIGS. 2a–c was a great improvement over prior art heat sinks, the construction of heatpipe 200 is cumbersome. Each component of heatpipe 200 must be individually fabricated, and the entire heatpipe 200 then assembled. That is, heatpipe base 202, pipe 204, horizontal fins 206 and pipe cap 210 must each be separately fabricated, and then the pieces are bonded together to form the final heatpipe 200. One of the most onerous steps in the fabrication/assembly process for heatpipe 200 is the attachment of horizontal fins 206 to pipe 204. After aligning each of the horizontal fins 206 with pipe 204, the horizontal fins 206 are bonded (usually with heat welding or a similar process) to pipe 204. This process is expensive, time consuming, and difficult to meet quality control parameters.
What is needed therefore is a device and method of manufacture for a heatpipe that is cheaper, faster, and easier to meet quality control standards.